1. Field of the Invention
Embodiments relate to the field of magnetic storage. More particularly, the present invention relates to a method, system and structure for patterning a magnetic substrate using ion implantation.
2. Discussion of Related Art
Conventional magnetic storage media may be fabricated using blanket magnetic layers that are written and read using a magnetic device to create and/or read small magnetic domains within the layer. As storage density scales to the Tbit/in2 range, microstructural limitations in blanket magnetic films, such as grain size effects, may limit the ability to magnetically write features of the size required to meet the storage density target. As an alternative to conventional magnetic storage coatings, bit patterned magnetic media have been studied in recent years.
In bit patterned magnetic recording media, individual islands of magnetic material may be isolated from one another, such that each island may represent one magnetic bit. This allows the bit boundary to be precisely defined by the physical edges of the patterned magnetic islands.
One proposed candidate for fabricating patterned magnetic recording media is the so-called nano-imprint lithography process. FIGS. 1a-e depict one implementation of nano-imprint lithography for patterning a magnetic layer. In nano-imprint lithography an imprint mold 12 is placed in contact with an imprintable medium 14 that is deposited on a magnetic layer 16, which in turn may be disposed on a substrate 18, as depicted in FIG. 1a. The imprintable medium may be a resist that flows under pressure exerted by the mold 12. In some cases, the resist may be heated in order to facilitate the imprint process. After release (FIG. 1b), the residual shape of the resist layer may resemble a negative relief of the mold 12. Any residual resist remaining in troughs may be removed (FIG. 1c), followed by a conventional etch step (FIG. 1d) to pattern the magnetic layer 16 by removing magnetic material in the exposed troughs. Subsequently, resist may be removed (FIG. 1e) leaving a patterned magnetic media structure comprising isolated structures, which may be planarized, if desired. In addition to the aforementioned nano-imprint lithography process, techniques have been developed in which self assembling block copolymers are used in conjunction with nano-imprint lithography. For example, nano-imprint lithography may be used to write a matrix of features on a surface which serves as a template of islands on which self-assembling block copolymers align. This process has been reported to yield more robust patterning of small features over a large area. It is to be noted that the above processes are typically performed in two dimensions within a plane of the substrate, resulting in a two dimensional array of isolated islands.
Although the nano-imprint lithography and related processes can in principle produce small isolated structures on the scale of tens of nm in lateral dimension, several challenges to its successful implementation remain. The aforementioned process steps involve removal of magnetic material, which may redeposit in other regions of the substrate, which may degrade planarity and may lead to damage of the sidewalls of bits during etch removal. In addition, it may be desirable or necessary to planarize the substrate after the isolated islands of magnetic material are created, adding to process complexity.
Other efforts to produce bit patterned magnetic structures have included the use of ion implantation to implant regions of a magnetic material to alter the properties in the implanted region and create isolated magnetic regions. By using a stencil mask or patterned photoresist, a pattern of ion implanted regions having the mask or photoresist pattern can be introduced into the magnetic layer. The ion implanted regions may have their original magnetic properties disrupted. This pattern of implantation can serve to separate one unimplanted region from other unimplanted regions, thereby forming isolated magnetic regions. However, the stencil mask efforts have involved relatively large bit patterns, where the lateral feature size is on the order of one micrometer, which is not suitable for future storage density requirements. The use of photoresist as a mask for bit patterning using implantation has also been investigated. However, photoresist materials generally exhibit less than optimal stability when subject to ion implantation. This instability may limit the ability to pattern very small dimensions using photoresist as an implantation mask.
In view of the above, it will be appreciated that there is a need to improve patterning technologies to create patterned magnetic media for high density storage.